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A Merco 35

By Dave Day.

At the 1959 Nationals I was approached by Bill Morley, who enquired whether I would be prepared to use an all-British 35 sized stunt motor. I had just placed third in the Gold Trophy with a stretched 'Calamity Jane' powered by an OS 35. I was aware that Bill had placed second the year before though, to be honest, I had no idea what motor he had used.

On 10th December 1959 I received a letter from Merco asking me formally if I would use their engines in 1960. I posted my answer the next day and received a brand new Merco 35 on the 16th. I had a Veco 'Thunderbird' kit and immediately started construction with the intention of using the Merco to power it. This was the original version (now known as the Mark I) which had an upright mounted engine.

The combination worked well and I used it to place third in the 1960 Team Trials for the world championships in Hungary and then fourth in the Gold Trophy. My other model at this time was a Veco 'Chief', fitted with the aforementioned OS. The 'T'bird' featured a very light fuselage construction and this soon began to break up. I designed a new fuselage to use the existing wing and tail, painted it blue and christened it 'Bluebird'. There was one significant difference - it had an inverted engine.

The motor never ran well in this model and gave constant problems in Hungary. I felt that I was under an obligation to use the motor and struggled on for the first two rounds, finally using the 'Chief' for the last round, when it was too late to retrieve things. Bill has told me since that he never thought that there was any obligation and he would have been happy if I had used the OS.

With many years of hindsight it is easy to see that my inverted cowl design did not allow adequate cooling. The kit design had a cowling (a Veco addition, Bob Palmer never used a cowling) which allowed a good flow of air straight through with plenty of outlet area. My inverted design was certainly lacking in outlet, with a bulkhead immediately behind the motor.

Early in 1960, I received a second motor from Bill. I had convinced myself at some stage (probably wrongly) that the stove enamelled red/orange head on the original motor was contributing to the cooling problems and told Bill of this. The second motor came without the enamel! It never ran as well, or as consistently, as the first.

The 'Bluebird' was quite successful for a while. With it's demise, the motor was fitted to a Warburton 'Tony', built from the Gremlin/Bradshaws kit. The model was very heavy and never competitive. I then produced a modified 'Thunderbird II' ('Spacebird') with several modifications, including a canted engine and internal muffler. This worked well, but the model had some trim difficulties, later attributed to the large wheel fairings that I had fitted. Meanwhile, I had produced a very successful model for the OS ('Iroquois V'), so the Merco was little used.

For a time the motor was fitted with a Merco R/C carburettor and used in a Frog 'Jackdaw' as part of the process of learning to fly R/C. The production R/C motor had a ventury that was machined to accept the carb. I modified the carb to fit into the stunt venturi. This worked quite well, but the demise of the 'Jackdaw' left the motor free to go back into the 'Spacebird'.

Refitting the standard needle assembly led to the discovery that the spraybar had two holes, diametrically opposite each other. At the time, it was generally felt that this was not a good arrangement and I fitted an OS needle and spraybar. The spring extension, a well-known feature of OS needles was replaced by a solid wire extension. This unit is still in use today.

We now arrive at 1969 when the 'Iroquois' was past it's sell-by date so the 'Spacebird' received the needed attention and won the Gold Trophy. It placed second in 1970 and won again in 1971.

Spacebird

Spacebird

By now I was heavily into R/C pylon racing and my stunt outings were mainly limited to an annual appearance in the Gold

In 1989, George Aldrich visited this country and a 'Nobler' contest was planned for the Nationals with a trophy to be presented by GMA himself. This was too good to miss, so I built a 'Nobler' for the event based on George's own plan of his original model (since kitted by Brodak) and powered by the Merco. The model was finished at 3 am on the Sunday morning and won the contest on it's first flight - in a thunderstorm! An interesting near recreation of Bill's Gold Trophy entry in 1958.

Original Nobler

Original Nobler

The direct result of this contest was the creation of a new Classic Stunt event to be flown at the Nats. That now tatty 'Nobler' and the Merco won for the next five years in a row (1990 - 95) making a total of 8 Nats wins for the Merco.

Fitted to yet another 'Nobler' (Green Box variety), the same motor finished third in the Classic event in 1997 and second in both 1999 and 2000, making a total of 12 finishes in the top three. It's difficult to say whether this particular motor is the most successful of the type, but it must be close.

Green box Nobler

Green box Nobler

An interesting note here is that the motor has always had a tendency to 'get the bit between it's teeth' and refuse to richen up once it has leaned out. This has led to some exciting fast flights. It took quite a while for the penny to finally drop that this was a temperature problem, caused by poor installation. On the 'Nobler' built in 1989, this was fully cured by cutting away most of the bulkhead behind the motor to allow air to enter the tank compartment.

When the same problem occured with the 'Green box Nobler', I cursed myself for not remembering and repeated the exercise. Another complete cure.

Forty plus years of hard contest flying have left some scars and the motor certainly looks well used. The pictures below show it as it now looks after removal from the severed nose of the above 'Nobler' which was broken in late 2000.

Merco 35 Merco 35

Feeling rather guilty about it's appearance I added up it's complete contest record:
Number of stunt contests flown: 107
Number of wins: 24
Add to that one second place in a Rat Race!

Thank you Bill.

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